Refrigeration systems are known for use with laboratory refrigerators and freezers of the type known as “high performance freezers,” which are used to cool their interior storage spaces to relatively low temperatures such as about −30° C. or lower, for example. One type of high performance freezer is known as an “ultra-low temperature freezer” (“ULT”), which is used to cool its inner storage chamber to relatively low temperatures such as about −80° C. or lower, for example.
Known refrigeration systems of this type include two stages circulating respective first and second refrigerants. The first stage receives energy (i.e., heat) from the cooled space (e.g., a cabinet inner chamber) through an evaporator circulating the first refrigerant, while the second refrigerant of the second stage transfers heat energy to the surrounding environment. Heat is transferred from the first refrigerant to the second refrigerant through a heat exchanger that is in fluid communication with the two stages of the refrigeration system. Alternatively, other known refrigeration systems used with high performance freezers only include one refrigeration stage with a condenser and an evaporator, such as when the cooling requirements in the freezer are less demanding.
In order to maximize a cooled space within these high performance freezers, the freezer has been provided with a rectangular box shaped cabinet. These box shaped cabinets include a door along at least one side wall for providing access into the inner chamber of the cabinet. Conventional doors are generally pivotally coupled to the cabinet and therefore require significant floor space or clearance to fully open the door. Additionally, opening these pivotal doors generally exposes the entire inner chamber to the exterior environment for the duration of the door opening. Especially when using a two-stage cascade refrigeration system in an ultra-low temperature freezer, exposing the entire inner chamber to the exterior environment adds significant heat energy into the inner chamber that requires a relatively lengthy period of time for the refrigeration system to recover to a desired temperature following the door re-closing.
Furthermore, it can be difficult to access items stored in the back of the inner chamber of these rectangular box shaped freezers. Even when improvements such as slide-out storage racks are provided in the cabinet to permit easier access to such stored items, the movement and replacing of these storage racks increases the total time that the door is opened and the inner chamber is exposed to the exterior environment. As described above, this arrangement therefore increases the amount of time that the refrigeration system requires to establish a desired temperature within the inner chamber.
There is a need, therefore, for a freezer that reduces the floor space required for the freezer and that improves the accessibility of items stored in all locations within the cabinet of the freezer.